The emphasis of this proposed research program is placed on obtaining four major objectives. These include the determination of the relative contribution of the anorexic and CNS stimulant actions of the psychomotor stimulants to their reinforcing efficacy. The reinforcing, anorexic, and stimulatory thresholds for intravenous administration of cocaine, chlorphentermine, phenmetrazine, methylphenidate, diethylproprion and methamphetamine will be ascertained for Rhesus monkeys. Secondly, the delineation of the primary mechanism which limits or restricts primate psychomotor stimulant self-administration behavior will be ascertaind. More specifically, it will be determined using several procedures, including a punishment paradigm, whether the rate of cocaine self-administration is determined by aversive or nonspecific behavioral disruptive actions of the drug. As a corollary, the mechanism whereby atropine and chlorpromazine facilitate self-administration of stimulants will be investigated. Thirdly, several procedures (progressive ratio, conditioned reinforcement and conflict) will be studied in an attempt to ascertain the relative reinforcing efficacy, i.e., abuse potential, of the substances listed above. Finally, the effects of manipulating several social and environmental variables purported to be operating in the stimulant abusing subculture will be determined. Among these variables manipulated will be the social structure of a group of subjects sharing drug access and drug availability. Furthermore symptoms similar to those seen in clinical mental depression will be produced in primates via social isolation. The effects of these manipulations on stimulant self-administration will be ascertained.